Crashing cars is expensive; the aim of the project is to make simulated
car crashes more accurate so that fewer tests need to be done on real cars.

My project is concerned with accurately measuring the properties of the
materials used to construct car interiors and crash test dummies, in order
to improve the accuracy of the interactions between them.

The difficulty is that these properties are dependent on strain rate, and
so to determine how the materials will behave in crashes they must be tested
at the speeds encountered during crash tests, in the region of 50mph.

This has led to a number of experimental difficulties, the tests last only
about 2.5mS, much faster than the response time of hydraulic valves, and
orders of magnitude faster than hydraulic systems. The machine needs to
exert forces of around 10kN at velocities of 20m/s. Simple mechanics shows
that this is an instanteneous power of 200kW.

The solution chosen was to use a cam operated device, incorporating a large
flywheel to provide the instantaneous power required.

The motor spins the 125kg flywheel at between 40 and 3000rpm. Once up to
speed a PC closes a relay, activating the pneumatic clutch which connects
the cam to the flywheel. As the bottom platten rises it's position is measured
by a capacitative transducer, and the compressive load is measured by the
load cell. Load and displacement information is stored by the PC along with
an internally generated time log.